1. Field of the Invention
The present invention relates to an apparatus for manufacturing dual filter plugs for cigarettes and, more particularly, to an apparatus suitable for manufacturing and feeding dual filter plugs to a production machine for filter cigarettes and a method of manufacturing and feeding the dual filter plugs.
2. Description of the Related Art
One-half of a filter plug or a filter tip is attached to one end of cigarette. The filter tip not only prevents shredded tobacco in the cigarette from entering into a mouth of a smoker during smoking, but also improves enjoyment of smoking.
A filter tip is generally, a plain filter tip. This plain filter tip is made of acetate fibers. A typical apparatus for manufacturing filter plugs will be described briefly below. The apparatus comprises drums of different types, each drum having grooves for continuously feeding one elongated plain filter rod, means for cutting the plain filter rod into filter plugs having a length twice that of the filter tip required for each cigarette, and means for aligning the filter plugs along the convey direction. The filter plugs are supplied from the filter manufacturing apparatus to a so-called wrapping machine. The wrapping machine will be described briefly below. Each filter plug is located between two adjacent series-aligned cigarettes. Chip paper is wound around these cigarettes and the filter plug to obtain two cigarettes with a double-length filter tip. The double-length filter tip is cut at the central position. Therefore, two cigarettes each with a plain filter tip are obtained.
A dual filter tip is also known as a cigarette filter in addition to the plain filter described above. A dual filter plug having a length twice that of the dual filter tip is obtained by combining a plain filter element consisting of only acetate fibers and a charcoal filter element obtained by mixing active carbon or the like in the plain filter element. For supplying the dual filter plugs from the filter manufacturing apparatus to the wrapping machine, if dual filter rods, each of which is made of the plain filter elements and the charcoal filter elements alternately arranged and connected to each other, are prepared in place of the plain filter rods, the filter manufacturing apparatus can be used without modifications.
A dual filter manufacturing apparatus disclosed in U.S. Pat. No. 4,321,050 comprises two feed units each having the same construction as that of the above filter manufacturing apparatus, and a coupling unit. In this known dual filter manufacturing apparatus, individual plain filter plugs are formed from a plain filter rod by one feed unit, and charcoal filter plugs are formed from a charcoal filter rod by the other feed unit. The resultant plain and charcoal filter plugs are received by the coupling unit. In the coupling unit, each charcoal filter plug is divided into two tips, and half-length charcoal filter tips are linearly aligned with a plain filter plug at both ends thereof, thereby obtaining double-length dual filter plugs.
As described above, when dual filter rods are prepared and dual filter plugs are to be manufactured by one filter manufacturing apparatus, an another apparatus for manufacturing dual filter rods is required in addition to the above filter manufacturing apparatus. Further, the another apparatus for manufacturing the dual filter rods needs a first filter paper to be wound around the plain filter elements and charcoal filter elements for obtaining the dual filter rod. For this reason, in the wrapping machine, when a tip paper or a second filter paper is wound around the double-length filter plug and two cigarettes to couple them, first filter paper and second filter paper overlap on the surface of the filler element. Therefore, the number of members for manufacturing dual filter cigarettes is increased to result in high manufacturing cost.
The filter manufacturing apparatus in the above U.S. patent is free from the above drawback. However, since two feed units are used, the number of grooved drums as constituting components of the respective feed units is greatly increased in the filter manufacturing apparatus as a whole. Therefore, the filter manufacturing apparatus becomes bulky and its mechanism is inevitably complicated.